1. Field of the Invention
This invention relates to an apparatus for stretching a plastic raw material such as bread dough, confectionery dough or any other material. More particularly, it relates to such apparatus whereby an effective stretching of the plastic raw material can be achieved by moving it past the apparatus and the stretching can be repeated by reversing the direction of movement of the dough to be stretched.
2. Description of the Prior Art
In the past, when thick dough was to be rolled into a thin dough strip in a dough stretching operation, a pair of opposing rollers have been rotated in reverse directions so that they move in the same direction as that of movement of dough where it comes into contact with the rolls, thereby imparting a stretching pressure to the dough. Such a process squeezes the dough. However, squeezing by merely imparting a stretching pressure as described above is not so effective for achieving the purpose of stretching viscoelastic material such as dough, because the squeezing pressure causes turbulent flows of dough resulting in an uneven tissue of the dough.
Another prior art apparatus has been such that dough is placed on conveying devices which are driven at different speeds, and rollers disposed thereabove for rotation along an orbit and revolution on their own axes make rolling movement in the traveling direction of the conveying devices where the dough touches the rollers, thereby stretching the dough. Such an apparatus obviates the difficulties encountered in the use of the abovementioned pair of rollers. However, in such an apparatus, dough is conveyed in one direction only.
In contrast to such prior art apparatus, this invention provides an apparatus where dough can be supplied in two directions so that the dough can be repeatedly stretched back and forth to conveniently achieve a high stretching effect.